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Top 10 List of Week 01

1. OS Virtualization

   7 Types of Virtualization:

   1. OS : The most common form, involves putting multiple instances of an OS into a machine.
   2. App-Server : Balance workload of a server
   3. App : Run applications on a ‘cloud’
   4. Administrative : Segmented admin roles through group and user policies
   5. Network : Manage IPs
   6. Hardware : Chunks of machine are partitioned to do specific tasks.
   7. Storage : Array of servers managed by a virtual storage system.

2. Virtual Memory and Demand Paging

   Virtual memory is a memory management technique that adds virtual memory to available memory, so that your system looks to have more memory than it actually does. That virtual memory is actually the memory of the hard disk which is then mapped to physical memory. Demand paging is the swapping process of virtual memory to the RAM. The data is not copied to the RAM till it is demanded by a progr

3. Virtual File Systems

   A virtual file system is programming that forms an interface between an operating system’s kernel and a more concrete file system. It serves as an abstraction layer that gives apps access to different types of file systems and local and network storage devices.

4. Hypervisors

   A hypervisor (or virtual machine monitor, VMM, virtualizer) is computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called a host machine, and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems.

5. Costs of Virtualization

   Many businesses find virtualization to be a cost-effective alternative to purchasing new hardware. Previously, it was necessary to allocate a new server for new applications. Now, virtual servers can run multiple operating systems and applications, eliminating hardware costs and optimizing software deployment and data backup.

6. Emulation vs. Isolation

   When a device is being emulated, a software-based construct has replaced a hardware component. With emulation, since an entire machine can be created as a virtual construct, there are a wider variety of opportunities, but with the aforementioned emulation penalty. But, emulation makes it possible to, for example, run programs designed for a completely different architecture on an x86 PC. With virtualization, the virtual machine uses hardware directly, although there is an overarching scheduler. As such, no emulation is taking place, but this limits what can be run inside virtual machines to operating systems that could otherwise run atop the underlying hardware. That said, this method provides the best overall performance of the two solutions.

7. Cloud Services

   The 4 Different Types of Cloud Computing Services:

   • Infrastructure as a Service (IaaS) : Provides a completely virtualized computing infrastructure that is provisioned and managed over the internet.
   • Platform as a Service (PaaS) : Provides the framework needed to build, test, deploy, manage, and update software products.
   • Software as a Service (SaaS) : A fully-developed software solution ready for purchase and use over the internet on a subscription basis.
   • Function as a Service (FaaS) : Often known as serverless computing, FaaS allows customers to execute code responsively without having to allocate processing resources ahead of time.

8. Bash Shell Scripting

   • Bash : Bash is a command language interpreter. It is widely available on various operating systems and is a default command interpreter on most GNU/Linux systems. The name is an acronym for the ‘Bourne-Again SHell’.
   • Shell : Shell is a macro processor which allows for an interactive or non-interactive command execution.
   • Scripting : Scripting allows for an automatic commands execution that would otherwise be executed interactively one-by-one.

   Learning Bash was a lot of fun as it was a new programming language for me to learn which was very interactive and could do alot of stuff with a relatively simple syntax.

9. Unix CLI

   A command-line interface (CLI) processes commands to a computer program in the form of lines of text. The program which handles the interface is called a command-line interpreter or command-line processor. Operating systems implement a command-line interface in a shell for interactive access to operating system functions or services. Using Bash Shell Scripting I could automate the process of using a CLI.

10. REGEX (Regular Expressions)

An expression is a string of characters. Those characters having an interpretation above and beyond their literal meaning are called metacharacters. Regular Expressions are sets of characters and/or metacharacters that match (or specify) patterns.

A Regular Expression contains one or more of the following:

• A character set. These are the characters retaining their literal meaning. The simplest type of Regular Expression consists only of a character set, with no metacharacters.
• An anchor. These designate (anchor*) the position in the line of text that the RE is to match. For example, ^, and $ are anchors.
• Modifiers. These expand or narrow (modify) the range of text the RE is to match. Modifiers include the asterisk, brackets, and the backslash.

The main uses for Regular Expressions (REs) are text searches and string manipulation.